This invention relates generally to gas turbine engines, and more specifically to variable stator vane assemblies used with gas turbine engines.
At least some known gas turbine engines include a core engine having, in serial flow arrangement, a fan assembly and a high pressure compressor which compress airflow entering the engine, a combustor which bums a mixture of fuel and air, and low and high pressure turbines which each include a plurality of rotor blades that extract rotational energy from airflow exiting the combustor. At least some known high pressure compressors include a plurality of rows of circumferentially spaced rotor blades, wherein adjacent rows of rotor blades are separated by rows of variable stator vane (VSV) assemblies. More specifically, a plurality of variable stator vane assemblies are secured to the compressor casing wherein each VSV assembly includes an air foil that extends between adjacent rotor blades. The orientation of the VSV air foils relative to the compressor rotor blades is variable to control air flow through the compressor.
At least one known variable stator vane assembly includes a trunnion bushing that is partially positioned around a portion of a variable vane so that the variable vane extends through the trunnion bushing. The assembly is bolted onto the high pressure compressor stator casing with the trunnion bushing between the variable vane and the casing. However, over time, such VSV assemblies may develop possible gas leakage paths, such as between an outside diameter of the airfoil and an inside diameter of the bushing. In addition, another leakage path may develop between an outside diameter of the bushing and an inside diameter of the compressor stator case opening. Such leakage may result in failure of the bushing due to oxidation and erosion caused by the high velocity high temperature air. Furthermore, once the bushing fails, an increase in leakage past the stator vane occurs, which results in a compressor performance loss. In addition, the loss of the bushing allows contact between the vane and the casing which may cause wear and increase the engine overhaul costs.
In one aspect a method for assembling a variable vane assembly for a gas turbine engine including a casing is provided. The variable vane assembly includes a seal assembly and at least one variable vane that includes a platform and a trunnion, wherein the platform extends radially outwardly from the trunnion. The method comprises coupling a seal assembly journal bushing to the variable vane such that the journal bushing is against the trunnion to prevent contact between the trunnion and the engine casing, and wherein the journal bushing has a substantially constant diameter extending between a first end and a second end of the journal bushing, and positioning a first washer on the variable vane ledge to prevent contact between the variable vane assembly and the engine casing, wherein the first washer is substantially flat and contacts the seal assembly journal bushing. The method also comprises positioning the variable vane assembly within an opening extending through the engine casing, and such that variable vane assembly trunnion extends through the opening.
In another aspect of the present invention, a variable vane assembly for a gas turbine engine including a casing is provided. The variable vane assembly includes a variable vane including a platform and a trunnion. The platform extends outwardly from the trunnion and includes an outer wall defining an outer periphery of the platform, and a radially outer surface that extends from the outer wall to the trunnion. The variable vane assembly also includes a seal assembly including a journal bushing and a first washer. The journal bushing includes a first end, a second end, and a substantially cylindrical body extending between the first and second ends, such that a diameter of the body is substantially constant between the first and second ends. The journal bushing is in contact with the trunnion and is configured to prevent contact between the trunnion and the engine casing. The first washer is substantially flat and extends from the platform outer wall towards the trunnion, and is configured to prevent contact between the variable vane platform radially outer surface and the engine casing.
In a further aspect, a compressor for a gas turbine engine is provided. The compressor includes a rotor including a rotor shaft and a plurality of rows of rotor blades, and a casing that surrounds the rotor blades. At least one row of variable vanes is secured to the casing and extends between an adjacent pair of the plurality of rows of rotor blades. Each variable vane includes a platform and a trunnion. The platform includes an outer wall that defines an outer periphery of the platform, and a radially outer surface that extends from the outer wall to the trunnion. A seal assembly is configured to facilitate reducing air leakage through the casing at least one opening and includes a journal bushing and a first washer. The journal bushing includes a first end, a second end, and a substantially cylindrical body extending between the first and second ends, such that a diameter of the journal bushing body is substantially constant between the bushing first and second ends. The journal bushing is in contact with the variable vane ledge and is configured to prevent contact between the ledge and the casing. The first washer is substantially flat and extends from the platform outer wall towards the trunnion. The first washer is configured to prevent contact between the variable vane platform radially outer surface and the casing.